Gives an unit Herostatus.
This does not change the basevalues of the unit! It just removes the possibility of eventual XP-Upgrades (and removes existing XP-Upgrades), while the unit gets immune to any debuffcards. The card can be played, even if there are heros in play already, but the created Hero blocks other heros for the owning player to come into play.
To mark the units properly, maybe they should be named: "Heroic ..." (to make a difference to the real Heros with changed basevalues)
Gamewise i think, this card has potential as buff and as debuff. On the one hand you can immunize a superstrong unit of your own against eventual debuffs, on the other hand, you can block an eventual opponents hero from coming into play or nerf this massive Veteran arty destroying your position (since it would lose its whole XP Bonus)